Flame resistant polycarbonate/ABS moulding compounds resistant to stress cracking

ABSTRACT

Flame resistant, thermoplastic molding compounds containing 
     A) 40 to 98 parts by weight of an aromatic polycarbonate, 
     B) 3 to 50 parts by weight of a vinyl copolymer, 
     C) 0.5 to 40 parts by weight of a graft polymer, 
     D) 0.5 to 20 parts by weight of a mixture of 
     D.1) 10 to 90 wt. %, related to D) , of a monophosphorus compound of the formula (I) ##STR1## D.2) 90 to 10 wt. %, related to D), of an oligomeric phosphorus compound of the formula (II) ##STR2## and E) 0.05 to 5 parts by weight of a fluorinated polyolefin with an average particle diameter of 0.05 to 1000 μm, a density of 1.2 to 2.3 g/cm 3  and a fluorine content of 65 to 76 wt. %.

This application is a continuation of application Ser. No. 08/516,899filed on Aug. 18, 1995 now abandoned, which in turn is a continuation ofSer. No. 08/290,544, filed on Aug. 15, 1994 now abandoned.

The present invention relates to flame resistant polycarbonate/ABSmoulding compounds whose stress cracking resistance is substantiallyimproved by a combination of additives comprising a monophosphoruscompound and an oligomeric phosphorus compound.

EP-A 0 174 493 (U.S. Pat. No. 4,983,658) describes flameproofed polymerblends containing halogen prepared from an aromatic polycarbonate, agraft copolymer containing styrene, monophosphates and a specialpolytetrafluoroethylene formulation. While these blends do indeed haveadequate fire behaviour and mechanical properties, they may be deficientin stress cracking resistance.

U.S. Pat. No. 5,030,675 describes flame resistant, thermoplasticmoulding compounds prepared from an aromatic polycarbonate, ABS polymer,polyalkylene terephthalate together with monophosphates and fluorinatedpolyolefins as flame retardants. Good stress cracking resistance isaccompanied by deficiencies in notched impact strength, together withunsatisfactory thermal stability when exposed to elevated temperatures,such as for example during processing.

Diphosphates are known as flame retardants. JA 59 202 240 describes theproduction of such a product from phosphorus oxychloride, diphenols suchas hydroquinone or bisphenol A and monophenols such as phenol or cresol.These diphosphates may be used as flame retardants in polyamide orpolycarbonate. However, this publication contains no indication of anyimprovement in stress cracking resistance by adding the oligomericphosphate to polycarbonate moulding compounds in conjunction withpolyalkylene terephthalates. EP-A 0 363 608 (=U.S. Pat. No. 5,204,394)describes polymer blends prepared from an aromatic polycarbonate, aCopolymer or graft copolymer containing styrene, together witholigomeric phosphates as flame retardants. U.S. Pat. No. 5,061,745describes polymer blends prepared from an aromatic polycarbonate, ABSgraft copolymer and/or a copolymer containing styrene and monophosphatesas flame retardants. The stress cracking resistance of these blends isoften inadequate for the production of thin-walled casing components.

It has surprisingly now been found that flame resistantpolycarbonate/ABS moulding compounds with excellent stress crackingresistance may be produced if a combination of additives comprising amonophosphorus compound and an oligomeric phosphorus compound is added.Particularly elevated stress cracking resistance is achieved if theratio by weight of the monophosphorus compound to the oligomericphosphorus compound is within the range 90:10 to 10:90. These mouldingcompounds are particularly suitable for the production of thin-walledmouldings (computer equipment casing parts), where elevated processingtemperatures and pressures result in the exposure of the material usedto considerable stress.

The present invention provides flame resistant, thermoplastic mouldingcompounds prepared from

A) 40 to 98 parts by weight, preferably 50 to 95 parts by weight,particularly preferably 60 to 90 parts by weight of an aromaticpolycarbonate,

B) 3 to 50, preferably 5 to 40 parts by weight of a vinyl copolymerprepared from

B.1) 50 to 98, preferably 60 to 95 parts by weight of styrene,α-methylstyrene, ring-substituted styrenes, C₁ -C₈ alkyl methacrylates,C₁ -C₈ alkyl acrylates or mixtures thereof and

B.2) 50 to 2, preferably 40 to 5 parts by weight of acrylonitrile,methacrylonitrile, C₁ -C₈ alkyl methacrylates, C₁ -C₈ alkyl acrylates,maleic anhydride, N-substituted maleimides and mixtures thereof,

C) 0.5 to 40 parts by weight, preferably 1 to 20 parts by weight,particularly preferably 2 to 12 parts by weight of a graft polymer,

D) 0.5 to 20 parts by weight, preferably 1 to 18 parts by weight,particularly preferably 2 to 15 parts by weight of a mixture of

D.1) 10 to 90 wt. %, preferably 12 to 50, in particular 14 to 40 wt. %,very particular 15 to 40 wt. % (related to the total quantity of D) of amonophosphorus compound of the formula (I) ##STR3## in which R¹, R² andR³ mutually independently mean optionally halogenated C₁ -C₈ alkyl, C₆-C₂₀ aryl or C₇ -C₁₂ aralkyl

m means 0 or 1 and

n means 0 or 1 and

D.2) 90 to 10 wt. %, preferably 88 to 50, in particular 86 to 60 wt. %,very particular 85 to 60 wt. % (related to the total amount of D) of anoligomeric phosphorus compound of the formula (II) ##STR4## in which R⁴,R⁵, R⁶, R⁷ mutually independently mean C₁ -C₈ alkyl, C₅ -C₆ cycloalkyl,C₆ -C₁₀ aryl or C₇ -C₁₂ aralkyl,

n mutually independently mean 0 or 1,

y means 1 to 5 and

X means a mono- or polycyclic aromatic residue with 6 to 30 C atoms,

and

E) 0.05 to 5 parts by weight, preferably 0.1 to 1 part by weight,particularly preferably 0.1 to 0.5 parts by weight of a fluorinatedpolyolefin with an average particle diameter of 0.05 to 1000 μm, adensity of 1.2 to 2.3 g/cm³ and a fluorine content of 65 to 76 wt. %.

The sum of all the parts by weight A+B+C+D+E is 100.

COMPONENT A

Suitable component A thermoplastic, aromatic polycarbonates according tothe invention are those based on diphenols of the formula (III) ##STR5##in which A is a single bond, C₁ -C₅ alkylene, C₂ -C₅ alkylidene, C₅ -C₆cycloalkylidene, --S-- or --SO₂ --,

B is chlorine, bromine,

q is 0, 1 or 2 and

p is 1 or 0

or alkyl-substituted dihydroxyphenylcycloalkanes of the formula (IV),##STR6## in which R⁸ and R⁹ mutually independently mean hydrogen,halogen,

preferably chlorine or bromine, C₁ -C₈ alkyl, C₅ -C₆ cycloalkyl, C₆ -C₁₀aryl, preferably phenyl, and C₇ -C₁₂ aralkyl, preferably phenyl-C₁ -C₄-alkyl, in particular benzyl,

m means an integer of 4, 5, 6 or 7, preferably 4 or 5,

R¹⁰ and R¹¹ mean, individually selectable for each Z, and mutuallyindependently hydrogen or C₁ -C₆ alkyl

and

Z means carbon, provided that on at least one Z atom, R¹⁰ and R¹¹simultaneously mean alkyl.

Suitable diphenols of the formula (III) are, for example, hydroquinone,resorcinol, 4,4'-dihydroxydiphenyl, 2,2-bis-(4-hydroxyphenyl) propane,2,4-bis-(4-hydroxyphenyl)-2-methylbutane,1,1-bis-(4-hydroxyphenyl)-cyclohexane,2,2-bis-(3-chloro-4-hydroxyphenyl) propane, 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)propane.

Preferred diphenols of the formula (III) are2,2bis-(4-hydroxyphenyl)propane,2,2-bis-(3,5-dichloro-4-hydroxyphenyl)propane and1,1-bis-(4-hydroxyphenyl)-cyclohexane.

Preferred diphenols of the formula (IV) are1,1-bis-(4-hydroxyphenyl)-3,3-dimethylcyclohexane,1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and1,1-bis-(4-hydroxyphenyl)-2,4,4-trimethylcyclopentane.

Both homopolycarbonates and copolycarbonates are suitable polycarbonatesaccording to the invention.

Component A may also be a blend of the thermoplastic polycarbonatesspecified above.

Polycarbonates may be produced in a known manner from diphenols withphosgene using the phase interface process or with phosgene using thehomogeneous phase process, the so-called pyridine process, whereinmolecular weight may be adjusted in a known manner with an appropriatequantity of known chain terminators.

Suitable chain terminators are, for example, not only phenol,p-chlorophenol, p-tert.-butylphenol or 2,4,6-tribromophenol, but alsolong-chain alkylphenols such as 4-(1,3-tetramethylbutyl)phenol accordingto DE-OS 2 842 005 (Le A 19 006) or monoalkylphenol or dialkylphenolwith a total of 8 to 20 C atoms in the alkyl substituents according toGerman patent application P 3 506 472.2 (Le A 23 654), such as3,5-di-tert.-butylphenol, p-iso-octylphenol, p-tert.-octylphenol,p-dodecylphenol and 2-(3,5-dimethylheptyl)phenol and4-(3,5-dimethylheptyl)phenol.

The quantity of chain terminators is in general between 0.5 and 10 mol.%, related to the sum of the diphenols of the formulae (III) and/or (IV)used in each case.

Suitable polycarbonates A according to the invention have averagemolecular weights (M_(W), weight average, measured for example byultracentrifugation or light scattering) of 10,000 to 200,000,preferably of 20,000 to 80,000.

Suitable polycarbonates A according to the invention may be branched ina known manner, in particular preferably by incorporation 0.05 to 2 mol.%, related to total quantity of diphenols used, of tri- or higherfunctional compounds, for example those with three or more phenolicgroups.

In addition to bisphenol A homopolycarbonate, preferred polycarbonatesare copolycarbonates of bisphenol A with up to 15 mol. %, related to thetotal molar quantities of diphenols, of2,2-bis-(3,5-dibromo-4-hydroxyphenyl)propane and the copolycarbonates ofbisphenol A with up to 60 mol. %, related to the total molar quantitiesof diphenols, of 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethyl-cyclohexane.

The polycarbonates A may be partially or entirely replaced with aromaticpolyester-carbonates.

COMPONENT B

Component B vinyl copolymers which may be used according to theinvention are those prepared from at least one monomer of the group:styrene, α-methylstyrene andr ring-substituted styrenes, C₁ -C₈ alkylmethacrylate, C₁ -C₈ alkyl acrylate (B.1) with at least one monomer fromthe group: acrylonitrile, methacrylonitrile, C₁ -C₈ alkyl methacrylate,C₁ -C₈ alkyl acrylate, maleic anhydride and/or N-substituted maleimide(B.2).

C₁ -C₈ alkyl acrylates or C₁ -C₈ alkyl methacrylates are esters ofacrylic or methacrylic acids respectively with monohydric alcohols with1 to 8 C atoms. Methyl methacrylate, ethyl methacrylate and propylmethacrylate are particularly preferred. Methyl methacrylate is cited asa particularly preferred methacrylic acid ester. Thermoplasticcopolymers of a composition according to component B may be produced assecondary products of graft polymerisation during production ofcomponent C, particularly if large quantities of monomers are graftedonto small quantities of rubber. The quantity of copolymer B to be usedaccording to the invention does not include these secondary products ofgraft polymerisation.

The component B copolymers are resinous, thermoplastic and contain norubber.

The thermoplastic copolymers B contain 50 to 98, preferably 60 to 95parts by weight of B.1 and 50 to 2, preferably 40 to 5 parts by weightof B.2.

Particularly preferred copolymers B are those prepared from styrene withacrylonitrile and optionally methyl methacrylate, from α-methylstyrenewith acrylonitrile and optionally methyl methacrylate or from styreneand α-methylstyrene with acrylonitrile and optionally methylmethacrylate.

The component B styrene/acrylonitrile copolymers are known and may beproduced by free-radical polymerisation, in particular by emulsion,suspension, solution or bulk polymerisation. The component B copolymerspreferably have molecular weights M_(W) (weight average, determined bylight scattering or settling) of between 15,000 and 200,000.

Particularly preferred copolymers B according to the invention are alsorandom copolymers of styrene and maleic anhydride, which may be producedfrom the corresponding monomers by continuous bulk or solutionpolymerisation with incomplete conversion.

The proportions of the two components in the suitable randomstyrene-maleic anhydride copolymers according to the invention may bevaried within a wide range. The preferred maleic anhydride content isbetween 5 and 25 wt. %.

The molecular weights (number average, M_(n)) of the suitable componentB random styrenealeic anhydride copolymers according to the inventionmay vary over a wide range. A range of 60,000 to 200,000 is preferred.An intrinsic viscosity of 0.3 to 0.9 is preferred for these products(measured in dimethylformamide at 25° C.; see Hoffmann, Kromer, Kuhn,Polymeranalytik I, Stuttgart 1977, p. 316 et seq.).

Instead of styrene, the vinyl copolymers B may also containring-substituted styrenes such as p-methylstyrene, vinyltoluene,2,4-dimethylstyrene, and other substituted styrenes such asα-methylstyrene.

COMPONENT C

The graft polymers C) comprise, for example, graft copolymers withrubber-elastic properties, which are substantially obtainable from atleast two of the following monomers: chloroprene, 1,3-butadiene,isoprene, styrene, acrylonitrile, ethylene, propylene, vinyl acetate and(meth)acrylic acid esters with 1 to 18 C atoms in the alcohol component;i.e. polymers as are, for example, described in Methoden der OrganischenChemie (Houben-Weyl), vol. 14/1, Georg Thieme Verlag, Stuttgart 1961, p.393-406 and in C. B. Bucknall, Toughened Plastics, Appl. SciencePublishers, London 1977. Preferred polymers C) are partially crosslinkedand have a gel content of above 20 wt. %, preferably of above 40 wt. %,in particular above 60 wt. %.

Preferred graft polymers C) comprise graft copolymers prepared from:

C.1) 5 to 95, preferably 30 to 80 parts by weight of a mixture of

C.1.1) 50 to 95 parts by weight of styrene, α-methylstyrene, halogen ormethyl ring-substituted styrene, C₁ -C₈ alkyl methacrylate, inparticular methyl methacrylate, C₁ -C₈ alkyl acrylate, in particularmethyl acrylate, or mixtures of these compounds and

C.1.2) 5 to 50 parts by weight of acrylonitrile, methacrylonitrile, C₁-C₈ alkyl methacrylates, in particular methyl methacrylate, C₁ -C₈ alkylacrylate, in particular methyl acrylate, maleic anhydride, C₁ -C₄ alkylor phenyl N-substituted maleimides or mixtures of these compounds on

C.2) 5 to 95, preferably 20 to 70 parts by weight of a polymer with aglass transition temperature of below -10° C.

Preferred graft polymers C) are, for example, polybutadienes,butadiene/styrene copolymers and acrylate rubbers grafted with styreneand/or acrylonitrile and/or (meth)acrylic acid alkyl esters; i.e.copolymers of the type described in DE-OS 1 694 173 (=U.S. Pat. No.3,564,077); polybutadienes, butadiene/styrene or butadiene/acrylonitrile copolymers, polyisobutenes or polyisoprenes grafted withacrylic or methacrylic acid alkyl esters, vinyl acetate, acrylonitrile,styrene and/or alkylstyrenes, as are, for example, described in DE-OS 2348 377 (=U.S. Pat. No. 3,919,353).

Particularly preferred polymers C) are, for example, ABS polymers, asare for example described in DE-OS 2 035 390 (=U.S. Pat. No. 3,644,574)or in DE-OS 2 248 242 (GB patent 1,409,275).

Particularly preferred graft polymers C) are graft polymers obtainableby the grafting reaction of

I. 10 to 70, preferably 15 to 50, in particular 20 to 40 wt. %, relatedto the grafted product, of at least one (meth) acrylic acid ester or 10to 70, preferably 15 to 50, in particular 20 to 40 wt. % of a mixture of10 to 50, preferably 20 to 35 wt. %, related to the mixture, ofacrylonitrile or (meth)acrylic acid ester and 50 to 90, preferably 65 to80 wt. %, related to the mixture, of styrene onto

II. 30 to 90, preferably 50 to 85, in particular 60 to

80 wt. %, related to the grafted product, of a butadiene polymer with atleast 50 wt. %, related to II, butadiene residues as the graftingbackbone,

wherein the gel content of the grafting backbone II is at least 70 wt. %(measured in toluene), the degree of grafting G of the graft polymer C)is 0.15 to 0.55 and its average particle diameter d₅₀ 0.05 to 2,preferably 0.1 to 0.6 μm.

(Meth) acrylic acid esters I are esters of acrylic acid or methacrylicacid and monohydric alcohols with 1 to 18 C atoms. Methyl, ethyl andpropyl methacrylate are particularly preferred.

In addition to butadiene residues, the grafting backbone II may containup to 50 wt. %, related to II, of residues of other ethylenicallyunsaturated monomers, such as styrene, acrylonitrile, esters of acrylicor methacrylic acid with 1 to 4 C atoms in the alcohol component (suchas methyl acrylate, ethyl acrylate, methyl methacrylate, ethylmethacrylate), vinyl esters and/or vinyl ethers. The preferred graftingbackbone II consists of pure polybutadiene.

Since, as is known, the graft monomers are not necessarily entirelygrafted onto the grafting backbone, graft polymers C) according to theinvention are also taken to be those products obtained by polymerisationof the graft monomers in the presence of the grafting backbone.

The degree of grafting G describes the ratio by weight of graftedmonomers to the grafting backbone and is dimensionless.

The average particle size d₅₀ is the diameter both above and below whichare found 50 wt. % of the particles. This value may be determined byultracentrifuge measurements (W. Scholtan, H. Lange, Kolloid Z. & Z.Polymere 250 (1972), 782-796).

Particularly preferred graft polymers C) are also, for example, graftpolymers of

(a) 20 to 90 wt. %, related to C), of acrylate rubber with a glasstransition temperature of below -20° C. as the grafting backbone and

(b) 10 to 80 wt. %, related to C), of at least one polymerisable,ethylenically unsaturated monomer, the homo- or copolymers of which, ifformed in the absence of a), would have a glass transition temperatureof above 25° C., as the graft monomers.

The acrylate rubbers (a) of the polymers C) are preferably polymers ofacrylic acid alkyl esters, optionally with up to 40 wt. %, related to(a), of other polymerisable, ethylenically unsaturated monomers.Preferred polymerisable acrylic acid esters include C₁ -C₈ alkyl esters,for example methyl, ethyl, n-butyl, n-octyl and 2-ethylhexyl acrylate;halogenalkyl esters, preferably halogen-C₁ -C₈ -alkyl esters, such aschloroethyl acrylate, together with mixtures of these monomers.

To achieve crosslinking, monomers with more than one polymerisabledouble bond may be copolymerised. Preferred examples of crosslinkingmonomers are esters of unsaturated monocarboxylic acids with 3 to 8 Catoms and unsaturated monohydric alcohols with 3 to 12 C atoms orsaturated polyols with 2 to 4 OH groups and 2 to 20 C atoms, such as forexample ethylene glycol dimethacrylate, allyl methacrylate;polyunsaturated heterocyclic compounds, such as for example trivinyl andtriallyl cyanurate; polyfunctional vinyl compounds, such as di- andtrivinylbenzenes; but also triallyl phosphate and diallyl phthalate.

Preferred crosslinking monomers are allyl methacrylate, ethylene glycoldimethacrylate, diallyl phthalate and heterocyclic compounds containingat least 3 ethylenically unsaturated groups.

Particularly preferred crosslinking monomers are the cyclic monomerstriallyl cyanurate, triallyl isocyanurate, trivinyl cyanurate,triacryloylhexahydro-s-triazine, triallylbenzenes.

The quantity of crosslinking monomers is preferably 0.02 to 5, inparticular 0.05 to 2 wt. %, related to the grafting backbone (a).

In the case of cyclic crosslinking monomers with at least 3ethylenically unsaturated groups, it is advantageous to limit thequantity to below 1 wt. % of the grafting backbone (a).

Other than the acrylic acid esters, preferred polymerisable,ethylenically unsaturated monomers which may optionally be used toproduce the grafting backbone (a) are, for example, acrylonitrile,styrene, α-methylstyrene, acrylamides, vinyl-C₁ -C₆ -alkyl ethers,methyl methacrylate, butadiene. Preferred acrylate rubbers as thegrafting backbone (a) are emulsion polymers having a gel content of atleast 60 wt. %.

Further suitable grafting backbones are silicone rubbers with activegrafting sites, as are described in DE-OS 37 04 657, DE-OS 37 04 655,DE-OS 36 31 540 and DE-OS 36 31 539.

The gel content of the grafting backbone (a) is determined indimethylformamide at 25° C. (M. Hoffmann, H. Kromer, R. Kuhn,Polymeranalytik I & II, Georg Thieme Verlag, Stuttgart 1977).

The aqueous dispersions of graft polymer C) to be used for the preferredembodiment of coprecipitation with the tetrafluoroethylene polymer E)generally have solids contents of 25 to 60, preferably 30 to 45 wt. %.

COMPONENT D

The polymer blends according to the invention contain as flame retardanta mixture of a monophosphorus compound D.1) and an oligomeric phosphoruscompound D.2). Component D.1) is a phosphorus compound according to theformula (I) ##STR7## in which formula, R¹, R² and R³ mutuallyindependently mean optionally halogenated C₁ -C₈ alkyl, C₆ -C₂₀ aryl orC₇ -C₁₂ aralkyl

m means 0 or 1 and

n means 0 or 1.

The phosphorus compounds according to component D.1) which are suitableaccording to the invention are generally known (see, for example,Ullmanns Enzyklopadie der technischen Chemie, vol. 18, p. 301 et seq.1979; Houben-Weyl, Methoden der Organischen Chemie, vol. 12/1, p. 43;Beilstein, vol. 6, p. 177). Preferred substituents R^(m) to R^(s)comprise methyl, butyl, octyl, chloroethyl, 2-chloropropyl,2,3-dibromopropyl, phenyl, cresyl, cumyl, naphthyl, chlorophenyl,bromophenyl, pentachlorophenyl and pentabromophenyl. Methyl, ethyl,butyl, phenyl, the latter optionally substituted with methyl, ethyl,chlorine and/or bromine, are particularly preferred.

Preferred phosphorus compounds D.1) (formula (I)) comprise, for example,tributyl phosphate, tris-(2-chloroethyl) phosphate,tris-(2,3-dibromopropyl) phosphate, triphenyl phosphate, tricresylphosphate, diphenylcresyl phosphate, diphenyloctyl phosphate,diphenyl-2-ethylcresyl phosphate, tri-(isopropylphenyl) phosphate,halogen-substituted aryl phosphates, methylphosphonic acid dimethylester, methylphosphonic acid diphenyl ester, phenylphosphonic aciddiethyl ester, triphenylphosphine oxide and tricresylphosphine oxide.

Component D.2) is an oligomeric phosphorus compound of the formula (II).##STR8##

In the formula, R⁴, R⁵, R⁶, R⁷ mutually independently mean C₁ -C₈ alkyl,C₅ -C₆ cycloalkyl, C₆ -C₁₀ aryl or C₇ -C₁₂ aralkyl, C₆ -C₁₀ aryl or C₇-C₁₂ aralkyl being preferred. The aromatic groups R⁴, R⁵, R⁶, R⁷ may inthemselves be substituted with halogen or alkyl groups. Particularlypreferred aryl residues are cresyl, phenyl, xylenyl, propylphenyl orbutylphenyl, together with the brominated and chlorinated derivativesthereof.

X in the formula (II) means a mono- or polycyclic aromatic residue with6 to 30 C atoms. This residue is derived from diphenols such as, forexample, bisphenol A, resorcinol or hydroquinone or also the chlorinatedor brominated derivatives thereof.

The values of n in the formula (II) may mutually independently be 0 or1, n preferably equalling 1.

y may have values between 1 and 5, preferably between 1 and 2. Mixturesof various oligomeric phosphates may also be used as component D.2)according to the invention. In this case, y has an average value between1 and 5, preferably between 1 and 2.

The polymer blends according to the invention contain as flame retardanta mixture of D. 1) and D.2). The weight ratios of D.1) and D.2) have tobe chosen in such a manner to achieve a synergistic effect. The mixturegenerally consists of 10 to 90 wt. % of D.1) and 90 to 10 wt. % of D.2)(related to D) in each case). Particularly favourable properties areachieved in the preferred and particularly preferred range of about 12to 50 and 14 to 40 wt. % of D.1) and 88 to 50 wt. % and 86 to 60 wt. %of D.2). Very particul- arly preferred is the range of 15 to 40 wt. % ofD.1) and 85 to 60 wt. % of D.2).

COMPONENT E

The fluorinated polyolefins E) are of high molecular weight and haveglass transition temperatures of above -30° C., generally of above 100°C., fluorine contents preferably of 65 to 76, in particular of 70 to 76wt. %, average particle diameters d₅₀ of 0.05 to 1000, preferably of0.08 to 20 μm. In general, the fluorinated polyolefins E) have a densityof 1.2 to 2.3 g/cm³. Preferred fluorinated polyolefins E) arepolytetrafluoroethylene, polyvinylidene fluoride,tetrafluoroethylene/hexafluoropropylene and ethylene/tetrafluoroethylenecopolymers. The fluorinated polyolefins are known (c.f. Vinyl andRelated Polymers by Schildknecht, John Wiley & Sons Inc., New York,1962, p. 484-494; Fluoropolymers by Wall, Wiley-Interscience, John Wiley& Sons Inc., New York, vol. 13, 1970, p. 623-654; Modern PlasticsEncyclopedia, 1970-1971, vol. 47, n° 10 A, October 1970, McGraw-HillInc., New York, p. 134 and 774; Modern Plastics Encyclopedia, 1975-1976,October 1975, vol. 52, n° 10 A, McGraw-Hill Inc., New York, p. 27, 28 &472 and U.S. Pat. Nos. 3,671,487, 3,723,373 and 3,838,092).

These polymers may be produced using known processes, such as forexample by polymerisation of tetrafluoroethylene in an aqueous mediumwith a free radical forming catalyst, for example sodium, potassium orammonium peroxydisulphate at pressures of 7 to 71 kg/cm² and attemperatures of 0° to 200° C., preferably at temperatures of 20° to 100°C. (For further details, see for example U.S. Pat. No. 2,393,967).Depending upon the form in which it is used, the density of thesematerials may be between 1.2 and 2.3 g/cm³ and average particle sizesbetween 0.05 and 1000

Preferred fluorinated polyolefins E) according to the invention aretetrafluoroethylene polymers with average particle diameters of 0.05 to20 μm, preferably of 0.08 to 10 μm, and a density of 1.2 to 1.9 g/cm³,which are preferably used in the form of a coagulated mixture ofemulsions of the tetrafluoroethylene polymers E) with emulsions of thegraft polymers C).

Suitable fluorinated polyolefins E) which may be used in powder form aretetrafluoroethylene polymers with average particle sizes of 100 to 1000μm and densities of 2.0 g/cm³ to 2.3 g/cm³.

In order to produce a coagulated mixture of C) and E), an aqueousemulsion (latex) of a graft polymer C) with an average latex particlediameter of 0.05 to 2 μm, in particular 0.1 to 0.6 μm, is first of allblended with a finely divided emulsion of a tetrafluoroethylene polymerE) in water with an average particle diameter of 0.05 to 20 μm, inparticular 0.08 to 10 μm; suitable tetrafluoroethylene polymer emulsionscustomarily have solids contents of 30 to 70 wt. %, in particular 50 to60 wt. %. The emulsions of the graft polymer C) have solids contents of25 to 50 wt. %, preferably of 30 to 45 wt. %.

The stated quantity in the description of component C) excludes theproportion of the graft polymer for the coagulated mixture of graftpolymer and fluorinated polyolefins.

In the emulsion mixture, the ratio by weight of graft polymer C) to thetetrafluoroethylene polymer E) is 95:5 to 60:40. The emulsion mixture isthen coagulated in a known manner, for example by spray drying, freezedrying or coagulation by adding inorganic or organic salts, acids, basesor organic, water-miscible solvents such as alcohols, ketones,preferably at temperatures of 20° to 150° C., in particular of 50° to100° C. If necessary, drying may be performed at 50° to 200° C,preferably 70° to 100° C.

Suitable tetrafluoroethylene polymer emulsions are customary commercialproducts offered for sale, for example, by the company DuPont as Teflon®30N.

The moulding compounds according to the invention may contain customaryadditives such as lubricants and mould release agents, nucleatingagents, antistatic agents, stabilisers, fillers and reinforcingmaterials, together with dyes and pigments. The filled or reinforcedmoulding compounds may contain up to 60, preferably 10 to 40 wt. %,related to the filled or reinforced moulding compound, of fillers and/orreinforcing materials. Glass fibre is the preferred reinforcingmaterial. Preferred fillers, which may also have a reinforcing effect,are glass beads, mica, silicates, quartz, talcum, titanium dioxide,wollastonite.

The moulding compounds according to the invention consisting ofcomponents A to E and optionally further known additives such asstabilisers, dyes, pigments, lubricants and mould release agents,fillers and reinforcing materials, nucleating agents together withantistatic agents are produced by mixing together the particularconstituents in a known manner and melt-compounding or melt-extrudingthem at temperatures of 200° C. to 330° C. in customary equipment, suchas internal kneaders, extruders and double screw extruders, whereincomponent E) is preferably used in the form of the already mentionedcoagulated mixture.

The present invention thus also provides a process for the production ofthermoplastic moulding compounds consisting of components A to E,optionally together with stabilisers, dyes, pigments, lubricants andmould release agents, fillers and reinforcing materials, nucleatingagents, together with antistatic agents, which is characterised in that,once components A to E, optionally together with stabilisers, dyes,pigments, plasticisers, fillers and reinforcing materials, lubricantsand mould release agents, nucleating agents and/or antistatic agents aremixed together, they are melt-compounded or melt-extruded in customaryequipment at temperatures of 200° to 330°, wherein component E ispreferably used in the form of a coagulated mixture with component C.The individual constituents may be mixed together in a known manner bothconsecutively and simultaneously, and both at approximately 20° C. (roomtemperature) and at higher temperatures.

The moulding compounds according to the present invention may be used toproduce mouldings of any kind. In particular, mouldings may be producedby injection moulding. Examples of articles which may be moulded are:casing parts of any kind, for example for household appliances such asjuice extractors, coffee machines, food mixers, for office equipment orcover plates for the construction sector and motor vehicle components.The moulding compounds are also used in electrical engineering becausethey have very good electrical properties.

The moulding compounds are particularly suitable for the production ofthin-walled mouldings (for example computer casing parts), which arerequired to exhibit particularly high notched impact strength and stresscracking resistance.

Another type of processing is the production of mouldings byblowmoulding or by thermaforming previously produced sheet or film.

EXAMPLES Component A

Bisphenol A based polycarbonate with a relative solution viscosity of1.26 to 1.28 measured in methylene chloride at 25° C. at a concentrationof 0.5 g/100 ml.

Component B

Styrene/acrylonitrile copolymer with a styrene/acrylonitrile ratio of72:28 and an intrinsic viscosity of 55 dl/g (measured indimethylformamide at 20° C).

Component C

Graft polymer of 45 parts by weight of styrene and acrylonitrile in aratio of 72:28 on 55 parts by weight of particulate, crosslinkedpolybutadiene rubber (average particle diameter d₅₀ =0.4 μm), producedby emulsion polymerisation.

Component D

D.1) triphenyl phosphate (Disflamoll® TP from Bayer AG) D.2)m-phenylene-bis(diphenylphosphate) (Fyroflex RDP from Akzo)

Component E

Tetrafluoroethylene polymer as a coagulated mixture prepared from anaqueous emulsion of SAN graft polymer according to C) and an aqueousemulsion of tetrafluoroethylene polymer. The ratio by weight of thegraft polymer C) to the tetrafluoroethylene polymer E) in the mixture is90 wt. % to 10 wt. %. The tetrafluoroethylene polymer emulsion has asolids content of 60 wt. % and average particle diameter is between 0.05and 0.5 μm. The SAN graft polymer emulsion has a solids content of 34wt. % and an average latex particle diameter of 0.4 μm.

PRODUCTION OF E

The emulsion of the tetrafluoroethylene polymer (Teflon 30 N fromDuPont) is blended with the SAN graft polymer emulsion C) and stabilisedwith 1.8 wt. %, related to polymer solids, of phenolic antioxidants. At85° to 95° C., the mixture is coagulated with an aqueous solution ofMgSO₄ (Epsom salts) and acetic acid at pH 4 to 5, filtered and washeduntil virtually free of electrolytes, the majority of the water is theneliminated by centrifugation and the product dried at 100° C. to give apowder. This powder may then be compounded with the other components inthe described equipment.

Production and Testing of Moulding Compounds According to the Invention

Components A to E were mixed together in a 3-1 internal kneader. Themouldings were produced on an Arburg 270 E injection moulding machine at260° C.

Stress cracking behaviour was determined on bars of dimensions 80×10×4mm, melt temperature 260° C. The test medium was a mixture of 60 vol. %toluene and 40 vol. % isopropanol. The test pieces were pre-stressed ona circular arc template (elongation 2.4%) and stored in the test mediumat room temperature. Stress cracking behaviour was determined byassessing cracking or failure as a function of length of exposure to thetest medium.

The composition of the tested materials and the results obtained aresummarised in the following table.

It may be seen from the table that the comparative examples 1 and 8 withpure component D.2) and D.1) respectively have distinctly lower stresscracking resistance than examples 2 to 7 according to the invention.

                  TABLE                                                           ______________________________________                                        Composition and properties of moulding compounds                                                          Failure at                                               Components  parts by weight!                                                                       ε.sub.x = 2.4%                            Example  A      B      C    D.1   D.2  E     minutes!                         ______________________________________                                        1 (comparison)                                                                         67     10     7.5  --    10   3.5  3.4                               2        67     10     7.5  1     9    3.5  3.5                               3        67     10     7.5  1.5   8.5  3.5  4.7                               4        67     10     7.5  2     8    3.5  5.6                               5        67     10     7.5  3     7    3.5  4.7                               6        67     10     7.5  4     6    3.5  4.3                               7        67     10     7.5  5     5    3.5  3.4                               8 (comparison)                                                                         67     10     7.5  10    --   3.5  2.5                               ______________________________________                                    

We claim:
 1. Flame resistant, thermoplastic moulding compoundscontainingA) 40 to 98 parts by weight of an aromatic polycarbonate; B) 3to 50 parts by weight of a vinyl copolymer prepared fromB.1) 50 to 98parts by weight of styrene, α-methylstyrene, ring-substituted styrenes,C₁ -C₈ alkyl methacrylates, C₁ -C₈ alkyl acrylates or mixtures thereofand B.2) 50 to 2 parts by weight of acrylonitrile, methacrylonitrile, C₁-C₈ alkyl methacrylates, C₁ -C₈ alkyl acrylates, maleic anhydride,N-substituted maleimides and mixtures thereof; C) 0.5 to 40 parts byweight of a graft polymer prepared fromC.1) 5 to 95 parts by weight of amixture of C.1.1) 50 to 95 parts by weight of styrene, α-methylstyrene,halogen or methyl ring-substituted styrene, C₁ -C₈ alkyl methacrylate C₁-C₈ alkyl acrylate, or mixtures of these compounds and C.1.2) 5 to 50parts by weight of acrylonitrile, methacrylonitrile, C₁ -C₈ alkylmethacrylates, C₁ -C₈ alkyl acrylate, maleic anhydride, C₁ -C₄ alkyl orphenyl N-substituted maleimides or mixtures of these compounds on C.2) 5to 95 parts by weight of a polymer with a glass transition temperatureof below -10° C. D) 0.5 to 20 parts by weight of a mixture ofD.1) 14 to40 wt. %, related to D), of a monophosphorus compound of the formula (I)##STR9## in which R¹, R² and R³ are independently phenyl, cresyl, cumyl,naphthyl, chlorophenyl, bromophenyl, pentachlorophenyl orpentabromophenyl n means 1 andD.2) 86 to 60 wt. %, related to D), of anoligomeric phosphorus compound of the formula (II) ##STR10## in whichR⁴, R⁵, R⁶, R⁷ are independently cresyl, phenyl xylenyl , propylphenylor butylphenyl, or brominated or chlorinated derivatives thereof, nmeans 1, y has an average value of between 1 and 2, and x means aresidue derived from resorcinol or hydroquinone, and E) 0.05 to 5 partsby weight of a fluorinated polyolefin with an average particle diameterof 0.05 to 1000 μm, a density of 1.2 to 2.3 g/cm³ and a fluorine contentof 65 to 76 wt. %.
 2. Moulding compounds according to claim 1 containing50 to 95 parts by weight of an aromatic polycarbonate A.
 3. Moldingcompounds as according to claim 1 containing component D) in amounts ofmonophosphorus compound D.1) and an oligomeric phosphorus compound D.2)in combined amounts effective to improve stress cracking resistance. 4.Flame resistant thermoplastic molding compound according to claim 1containing additives selected from the group consisting of stabilizers,dyes, pigments, lubricants and mold release agents, fillers andreinforcing materials, nucleating agents and antistatic agents.
 5. Theflame resistant, thermoplastic molding compound of claim 1, wherein incomponent D.2. each of R⁴, R⁵, R⁶ and R⁷ are phenyl.
 6. A flameresistant thermoplastic molding compound having improved stressresistance, consisting essentially of:A) 40-98 parts by weight ofaromatic polycarbonate; B) 3-50 parts by weight of styrene/acrylonitrilecopolymer; C) 0.5 to 40 parts by weight of a graft polymer of styreneand acrylonitrile on particulate, crosslinked polybutadiene rubber; D)0.5 to 20 parts by weight of a mixture of:D.1.) 14 to 40%, based on D),of triphenyl phosphate; D.2.) 86 to 60%, based on D), ofm-phenylene-bis(diphenylphosphate); and E) 0.05 to 5 parts by weight oftetrafluoroethylene polymer.
 7. The molding compound of claim 6containing 50 to 95 parts of A), 5 to 40 parts of B), 2 to 12 parts ofC), 2 to 15 parts of D), and 0.1 to 0.5 parts of E).
 8. The moldingcompound of claim 7, containing 67 parts of A), 10 parts of B), 7.5parts of C), and 3.5 parts of E).
 9. Flame resistant, thermoplasticmounding compounds containingA) 40 to 98 parts by weight of an aromaticpolycarbonate; B) 3 to 50 parts by weight of a vinyl copolymer preparedfromB.1) 50 to 98 parts by weight of styrene, α-methylstyrene,ring-substituted styrenes, C₁ -C₈ alkyl methacrylates, C₁ -C₈ alkylacrylates or mixtures thereof and B.2) 50 to 2 parts by weight ofacrylonitrile, methacrylonitrile, C₁ -C₈ alkyl methacrylates, C₁ -C₈alkyl acrylates, maleic anhydride, N-substituted maleimides and mixturesthereof; C) 0.5 to 40 parts by weight of a graft polymer preparedfromC.1) 5 to 95 parts by weight of a mixture of C.1.1.) 50 to 95 partsby weight of styrene, α-methylstyrene, halogen or methylring-substituted styrene, C₁ -C₈ alkyl methacrylate C₁ -C₈ alkylacrylate, or mixtures of these compounds and C.1.2.) 5 to 50 parts byweight of acrylonitrile, methacrylonitrile, C₁ -C₈ alkyl methacrylatesC₁ -C₈ alkyl acrylate, maleic anhydride, C₁ -C₄ alkyl or phenylN-substituted maleimides or mixtures of these compounds on C.2) 5 to 95parts by weight of a polymer with a glass transition temperature ofbelow -10° C. D) 0.5 to 20 parts by weight of a mixture ofD.1) 10 to 90wt. %, related to D), of a monophosphorus compound of the formula (I)##STR11## in which R¹, R² and R³ mutually independently mean optionallyhalogenated C₁ -C₈ alkyl, C₆ -C₂₀ aryl or C₇ -C₁₂ aralkyl n means 1andD.2) 90 to 10 wt. %, related to D), of an oligomeric phosphoruscompound of the formula (II) ##STR12## in which R⁴, R⁵, R⁶, R⁷ aremutually independently cresyl, phenyl, xylenyl, propylphenyl orbutylphenyl, or brominated or chlorinated derivatives thereof n means 1,Y means an average value between 1 and 2, and X means a residue derivedfrom resorcinol or hydroquinone, and E) 0.05 to 5 parts by weight of afluorinated polyolefin with an average particle diameter of 0.05 to 1000μm, a density of 1.2 to 2.3 g/cm³ and a fluorine content of 65 to 76 wt.%.
 10. The moulding compound of claim 9, wherein component C) is one ormore of polybutadiene, butadiene styrene copolymer, acrylate rubber,polyisobutadiene, or polyisoprene.
 11. The moulding composition of claim9, wherein component C) is polybutadiene, butadiene/styrene copolymer,or mixtures thereof.